//#define _CRT_SECURE_NO_WARNINGS 1
//
//
////
//
#include<stdio.h>
int main()
{
	int x1 = 0, x2 = 0;
	int y1 = 0, y2 = 0;
	scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
	printf("%d", ((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2)));
	return 0;
}